Streptococcus porcorum sp. nov., isolated from domestic and wild pigs

Abstract

Seven isolates of an unidentified Gram-stain-positive, catalase-negative, coccus-shaped organism isolated from domestic and wild pigs were characterized by phenotypic and molecular-genetic methods. Based on cellular morphology and biochemical criteria, the isolates were tentatively assigned to the genus Streptococcus, although the organisms did not appear to correspond to any recognized species. Comparative 16S rRNA gene sequencing showed that the unknown bacterium was phylogenetically closely related to, but distinct from, Streptococcus suis (97.5 % 16S rRNA gene sequence similarity to the type strain). rpoB and sodA sequence analysis showed minimum interspecies divergence from phylogenetically close 16S rRNA gene sequence-based relatives of 13.8 and 18.6 %, respectively. DNA-DNA hybridization of a strain of the unidentified organism demonstrated 8-18 % reassociation with S. suis NCTC 10234(T). The novel bacterium could be distinguished from S. suis and other Streptococcus species using biochemical tests. On the basis of phenotypic and phylogenetic evidence, it is proposed that the unknown isolates from domestic and wild animals be assigned to a novel species of the genus Streptococcus, Streptococcus porcorum sp. nov. The type strain is 682-03(T) ( = CCUG 58479(T) = CECT 7593(T)).